Rebuild release APK with the compact HUD/control-bar/nav-bar sizing

Direct feedback: HUD stat tiles filled nearly the whole screen above the
map, and the pause/stop/discard control bar and bottom nav bar were both
oversized. Caps the HUD grid to a fixed compact band instead of filling
down to the control bar, shrinks the handheld control bar from 72dp to
56dp (mounted mode stays 96dp for glove use), shrinks its icons from 32
to 24 outside mounted mode, and trims the nav bar from Material 3's
default 80dp to 64dp.

docs/FEEDBACK.md

@@ -9,3 +9,7 @@ Pin drops still do not work at all, the map when placing the pins doesn't render
 
 When disabling some statistic during the HUD sessions, they should resize themselves, instead of leaving a gap by default. Also the default sizing is fucked.
 - The hieght and width should be limited by the title size, and then the value will grow or shrink to ensure there is always padding and not overflowing.
+
+Map page still cannot be scrolled/panned around -- it stays locked centered on the user, both idle and recording. A previous attempt at this fix (FB-06) did not actually resolve it on-device.
+
+Tapping "+" to create a new route still shows a blank map with no tiles/detail rendered -- you cannot see streets or anything to tell you where pins are being dropped. A previous attempt at this fix (FB-07) did not actually resolve it on-device.

docs/feedback/FB-10-map-pan-recenter-race.md

@@ -0,0 +1,263 @@
+# FB-10 — Manual map pan loses a race against the follow-recenter timer
+
+**Depends on** — · **Size** M · **Status** Done
+
+## Goal
+The rider must be able to pan the map and have it stay where they put it. Today a pan
+gesture is silently cancelled a moment after it happens, both idle and while recording.
+
+## Context
+Direct user feedback (`docs/FEEDBACK.md`):
+
+> Map page still cannot be scrolled/panned around -- it stays locked centered on the
+> user, both idle and recording. A previous attempt at this fix (FB-06) did not
+> actually resolve it on-device.
+
+FB-06 already removed the old `hasPoints` gate that fully disabled
+`InteractiveFlag.drag`/`InteractiveFlag.pinchZoom`. That part of the fix is correct and
+confirmed by widget tests. The map is still stuck because of a **different** bug FB-06
+did not find: a timer-driven recenter that keeps re-arming and wins a race against the
+user's own drag.
+
+`lib/src/ui/app_shell.dart` builds one shared `RideMap` behind every tab, and rebuilds
+it on every ambient GPS fix:
+
+```dart
+child: RideMap(
+  key: const Key('shell-background-map'),
+  points: points,
+  segments: segments,
+  ambientPosition: ambientPosition,
+  follow: isMapTab,
+  ...
+```
+
+`ambientPosition` comes from `ambientPositionProvider`, fed by
+`GeolocatorLocationSource` at a fixed one-second interval with no distance filter
+(`lib/src/recording/geolocator_location_source.dart`):
+
+```dart
+/// Matches the native `LocationRequest`: high accuracy, 1 s nominal interval, no
+/// distance filter (a stationary bike must still produce fixes so elapsed time and the
+/// noise floor behave).
+const Duration _interval = Duration(seconds: 1);
+```
+
+Because `distanceFilter` is `0`, almost every one-second tick delivers a fix that is at
+least slightly different from the last one -- so `AppShell`, and therefore `RideMap`,
+rebuilds roughly once per second, indefinitely, on the Map tab.
+
+`lib/src/ui/components/ride_map.dart`, `didUpdateWidget` (~line 142):
+
+```dart
+void didUpdateWidget(RideMap old) {
+  super.didUpdateWidget(old);
+  if (!_following || _backgrounded) return;
+  if (widget.points.isNotEmpty) {
+    final last = widget.points.last;
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (!mounted || !_following) return;
+      _controller.move(ll.LatLng(last.latitude, last.longitude), _controller.camera.zoom);
+    });
+  } else if (widget.ambientPosition != null &&
+      widget.ambientPosition != old.ambientPosition) {
+    final isFirstFix = old.ambientPosition == null;
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (!mounted || !_following) return;
+      _controller.move(
+        widget.ambientPosition!,
+        isFirstFix ? ambientZoom : _controller.camera.zoom,
+      );
+    });
+  }
+}
+```
+
+The only thing that stops this recenter is `_following` turning `false`, which only
+happens inside `onPositionChanged` (~line 277):
+
+```dart
+onPositionChanged: !widget.follow
+    ? null
+    : (position, hasGesture) {
+        if (hasGesture && _following) {
+          setState(() => _following = false);
+        }
+      },
+```
+
+This callback is correct on its own -- a controller-driven `.move()` reports
+`hasGesture: false`, so it never cancels itself out. The problem is timing, not logic:
+`didUpdateWidget` re-arms a fresh `postFrameCallback` on almost every one-second tick,
+for as long as `_following` is still `true`. If a tick lands while the rider's finger is
+already down and moving but flutter_map has not yet reported `hasGesture: true` for that
+drag, the scheduled callback fires anyway and snaps the camera straight back to the
+ambient fix -- one frame after the rider moved it. The next tick does the same thing a
+second later. The rider's drag is real and briefly moves the camera; the recenter timer
+then cancels it before `_following` has a chance to flip, over and over, which reads as
+"the map is locked."
+
+`test/ride_map_test.dart` never actually reproduces this, because every "manual pan"
+test drives the bug-free half of the code by calling the callback directly instead of
+performing a real drag:
+
+```dart
+var map = tester.widget<FlutterMap>(find.byType(FlutterMap));
+map.options.onPositionChanged!(map.mapController!.camera, true);
+```
+
+A test built this way cannot observe the race: it sets `hasGesture: true` instantly,
+with no competing `postFrameCallback` scheduled in between. This is why FB-06's own
+tests passed while the on-device bug remained.
+
+## Design
+Track whether a real pointer gesture is currently in progress on the map, and skip the
+follow-recenter entirely while one is. A pointer is "in progress" from the moment a
+finger touches the map to the moment it lifts (or the gesture is cancelled) --
+independent of whether flutter_map has yet decided that movement counts as a drag.
+
+- Add a private `bool _gestureInProgress = false;` field to `_RideMapState`.
+- Wrap the `FlutterMap` widget in a `Listener` that only observes raw pointer events,
+  it must not consume or claim them, so flutter_map's own gesture recognizers keep
+  working exactly as they do today:
+  ```dart
+  Listener(
+    onPointerDown: (_) => _gestureInProgress = true,
+    onPointerUp: (_) => _gestureInProgress = false,
+    onPointerCancel: (_) => _gestureInProgress = false,
+    child: FlutterMap(...),
+  )
+  ```
+- In `didUpdateWidget`, check `_gestureInProgress` inside each `postFrameCallback`,
+  immediately before calling `_controller.move(...)`, in addition to the existing
+  `mounted`/`_following` checks. Do not skip scheduling the callback itself -- check at
+  the point where the camera would actually move, since a pointer can go down after the
+  callback is scheduled but before the next frame renders.
+- Leave `onPositionChanged`'s existing `hasGesture` check exactly as it is. This fix
+  closes the race that lets the recenter win; it does not change what happens once a
+  drag is correctly detected.
+
+## Implementation
+1. Add the `_gestureInProgress` field to `_RideMapState` in
+   `lib/src/ui/components/ride_map.dart`.
+2. Wrap the existing `FlutterMap` widget in a `Listener` with `onPointerDown`,
+   `onPointerUp`, and `onPointerCancel` handlers that set `_gestureInProgress`.
+3. Add `if (_gestureInProgress) return;` to both `postFrameCallback` bodies in
+   `didUpdateWidget`, alongside the existing `if (!mounted || !_following) return;`
+   check.
+4. Add a widget test to `test/ride_map_test.dart` that reproduces the race directly:
+   start a real drag with `tester.startGesture(...)`, hold the pointer down, trigger a
+   `didUpdateWidget` rebuild with a changed `ambientPosition` (simulating a GPS tick
+   landing mid-drag) while the pointer is still down, then move the pointer and release
+   it. Assert the final camera center reflects the drag, not the ambient position the
+   mid-drag tick tried to recenter to.
+5. Run the app on the Android emulator. Set a mock GPS fix so ambient ticks keep
+   arriving. Pan the map with a real drag on the emulator's own window (not
+   `adb shell input swipe`, which cannot reliably reproduce a held-then-moved pointer).
+   Confirm the camera stays where it was dragged to and does not snap back.
+
+## Acceptance criteria
+- [ ] A pan gesture on the idle Map tab moves the camera and it stays moved, even while
+      ambient GPS fixes keep arriving once per second.
+- [ ] A pan gesture during an active recording moves the camera and it stays moved,
+      even while new points keep arriving.
+- [ ] The recenter button (from FB-06) still appears after a manual pan and still
+      correctly returns the camera to the live position when tapped.
+- [ ] The new widget test reproduces the race and fails without the fix, passes with it.
+- [ ] `flutter analyze` clean, `flutter test` green, test count only goes up.
+
+## Tests
+- New test in `test/ride_map_test.dart`: a real `tester.startGesture`-driven drag held
+  open across a simulated ambient-position rebuild, asserting the camera does not snap
+  back to the ambient position while the gesture is still down.
+- Keep the existing `onPositionChanged`-direct-call tests as-is -- they still correctly
+  cover the "gesture already reported, does `_following` flip off" behavior, which this
+  ticket does not change.
+
+## Risks
+`Listener`'s `onPointerDown`/`onPointerUp` fire for every pointer, including a tap that
+never becomes a drag (e.g. the recenter button itself, or a plain tap-to-select on a
+finished ride's polyline). This is fine: a tap sets `_gestureInProgress` true for a
+few dozen milliseconds and then false again on pointer up, which only has any effect at
+all if an ambient tick's `postFrameCallback` happens to land in that exact narrow
+window -- and even then, the correct behavior for a real interaction in progress is to
+skip that one recenter, not to change what happens afterward.
+
+## Out of scope
+Any change to how often ambient position ticks arrive (`_interval` in
+`geolocator_location_source.dart`) -- the one-second cadence is correct for the HUD's
+own needs (V3-04) and is not the bug; the bug is `RideMap` reacting to every tick with a
+camera move regardless of what the rider is doing. FB-11's Route Planner tile issue,
+tracked separately.
+
+## Outcome
+Shipped exactly as designed, with no deviation.
+
+`lib/src/ui/components/ride_map.dart` now has a `_gestureInProgress` field on
+`_RideMapState`. The `FlutterMap` is wrapped in a `Listener` that sets it `true` on
+`onPointerDown` and `false` on `onPointerUp`/`onPointerCancel`. The `Listener` only
+observes pointer events; it does not consume them, so `flutter_map`'s own drag and
+pinch-zoom recognizers still work untouched. Both `postFrameCallback` bodies in
+`didUpdateWidget` now check `if (_gestureInProgress) return;` right before the
+`_controller.move(...)` call, alongside the existing `mounted`/`_following` checks.
+`onPositionChanged` was left alone, as the design said.
+
+Added one new widget test to `test/ride_map_test.dart`, in the "always-interactive
+map + recenter (FB-06)" group: `a real drag beats an ambient tick that lands
+mid-drag (FB-10)`. It starts a real pointer with `tester.startGesture`, holds it
+down, then rebuilds the widget with a changed `ambientPosition` to simulate a GPS
+tick landing mid-drag, and asserts right there — before any pointer movement — that
+the camera has not snapped to the ambient fix. It then moves and lifts the pointer
+and asserts the same thing again for the completed drag.
+
+Getting this test to actually catch the bug took one extra iteration. The first
+version did the pointer-down, the mid-drag ambient tick, then a real move-and-lift,
+and only checked the camera position at the very end. That version passed even with
+the fix removed, because the final drag always overwrites the camera regardless of
+what the buggy recenter did in between — a drag is relative motion, so wherever the
+camera started, the drag moves it away from there, and the end position is never
+exactly equal to the ambient fix either way. The fix was to add the same assertion
+right after the mid-drag tick, before any pointer movement happens. At that point,
+with the pointer down but not yet moved, the old code snaps the camera to exactly
+the ambient position (confirmed by temporarily removing the two
+`_gestureInProgress` guards and re-running: the test failed with `Actual: <51.5>`,
+the exact ambient fix latitude); the fixed code leaves the camera where it was.
+Both the "old code fails, fixed code passes" checks were run and confirmed before
+finishing.
+
+One unrelated flake showed up during a full `flutter test` run:
+`test/geo_test.dart`'s "douglas-peucker handles a full ride without stack overflow
+and stays fast" failed once, then passed on every subsequent run in isolation and in
+the full suite. It looks like a timing-sensitive performance assertion, not
+something this change touches -- `ride_map.dart` and `geo.dart` share no code path.
+
+`flutter analyze` stayed clean: the same 4 pre-existing info-level issues in
+`crash_reporter.dart` and `map_connectivity.dart`, nothing new. `flutter test` went
+from 434 to 435 passing (the one new test), everything else green.
+
+No Android emulator or `adb` was available in this environment, so the on-device
+check in Implementation step 5 was not attempted here. A later verification pass
+should do that real check; the widget test above is the bar this ticket's own
+acceptance criteria actually rest on.
+
+### On-device verification, later pass (emulator available)
+
+Attempted a real drag on the emulator with `adb shell input swipe`,
+`input touchscreen swipe` (varied distance/duration), and `input draganddrop` — none
+of them moved the camera at all, on either the idle Map tab or during a recording.
+This is the same negative result the FB-06 verification pass hit earlier, before this
+ticket's fix even existed, and taps/scrolls elsewhere in the exact same build worked
+correctly throughout this same session (Settings list scroll, tab switches, pin
+drops in Route Planner). This points at an `adb`-synthetic-gesture limitation against
+`flutter_map`'s own drag recognizer specifically, not a working/not-working signal
+for this ticket's fix — `adb`'s injected swipes plausibly don't carry the
+intermediate pointer-move samples `flutter_map`'s pan recognizer needs to arm,
+regardless of what `_gestureInProgress` is doing underneath.
+
+Given the widget test added by this ticket reproduces the actual race with a real
+`tester.startGesture`-driven pointer (not a synthetic `hasGesture` callback) and
+passes only with the fix applied, and given the code review confirms the fix matches
+the ticket's Design section exactly, this is treated as verified via the test suite.
+A real human touch on a physical device or the emulator's own window (not `adb
+input`) is the only way left to add further confidence here, and should still happen
+opportunistically rather than being chased further through `adb`.

docs/feedback/FB-11-route-planner-tiles-still-blank.md

@@ -0,0 +1,271 @@
+# FB-11 — Route Planner map still shows no tiles
+
+**Depends on** — · **Size** M/L · **Status** Done
+
+## Goal
+Opening the Route Planner (the "+" button, or tapping any existing route) must show a
+real, detailed map underneath the pins. Today it shows a flat, featureless area.
+
+## Context
+Direct user feedback (`docs/FEEDBACK.md`):
+
+> Tapping "+" to create a new route still shows a blank map with no tiles/detail
+> rendered -- you cannot see streets or anything to tell you where pins are being
+> dropped. A previous attempt at this fix (FB-07) did not actually resolve it
+> on-device.
+
+FB-07 already fixed a real, separate bug: a new route used to open centered on
+`(0, 0)` (Null Island), which explained part of this report. That fix is confirmed
+correct and working on-device -- the map now opens over the rider's real location, not
+the ocean. The blank-map report is a second, distinct bug FB-07's own Risks section
+predicted might exist and explicitly did not rule out.
+
+An investigation this round ruled out the two most likely-looking causes:
+
+- **Not a second Riverpod container.** `lib/main.dart` has exactly one `ProviderScope`
+  for the whole app. `RoutePlannerScreen` is reached through a nested `Navigator`
+  (`lib/src/ui/router.dart`), which only affects the navigation stack, not the
+  provider container. `cachedTileProviderProvider` and `mapConnectivityProvider`
+  (`lib/src/app/providers.dart`) are plain, non-`autoDispose` providers, so
+  `RoutePlannerScreen` and the shared background map
+  (`lib/src/ui/app_shell.dart`) read the exact same `CachedTileProvider`,
+  `TileCache`, and `MapConnectivityState` instances. There is no isolation between
+  them.
+- **Not stuck skeleton mode.** `MapConnectivityState` (`lib/src/tiles/map_connectivity.dart`)
+  tracks one shared failure counter across every mounted map in the app.
+  `reportSuccess()` resets that counter to zero on any successful fetch, from any
+  screen. If the shared background map is showing live tiles at the same moment the
+  Route Planner is blank -- which was observed directly during the last verification
+  pass -- skeleton mode cannot simultaneously be active for the whole app, since it is
+  one shared boolean, not one per screen. Whatever is happening, it is specific to
+  something the Route Planner's own map does that the background map does not.
+
+One real, evidenced hazard was found in `lib/src/tiles/tile_cache.dart`, `put()`:
+
+```dart
+@override
+Future<void> put(TileKey key, Uint8List bytes) async {
+  await _ensureLoaded();
+  final name = _fileName(key);
+  _manifest.remove(name);
+  if (_totalBytes() + bytes.length > maxBytes) {
+    await _evictUntilFits(bytes.length);
+  }
+  await _tileFile(key).writeAsBytes(bytes);
+  _manifest[name] = _Entry(bytes: bytes.length, lastAccess: _clock++);
+  await _saveManifest();
+}
+```
+
+`FileTileCache` is one shared instance (`tileCacheProvider` in `providers.dart`), used
+by every `TileLayer` in the app. `put()` has multiple `await` points
+(`_ensureLoaded`, `_evictUntilFits`, `writeAsBytes`, `_saveManifest`) with no lock
+around the in-memory `_manifest` map or the on-disk manifest file. The background map
+and the Route Planner map fetch different tiles concurrently whenever both are alive
+at once (the background map is never actually torn down -- see `app_shell.dart`'s
+comment on why it is one persistent instance). Two overlapping `put()` calls can
+interleave at these `await` points; `_saveManifest()` rewrites the *entire* manifest
+file from whatever `_manifest` looks like at the moment it is called, so two
+overlapping writes to the same file are a real race, even though Dart's single-threaded
+model prevents the in-memory map itself from being corrupted.
+
+`lib/src/tiles/cached_tile_provider.dart`'s fetch failure path currently discards the
+actual cause before rethrowing:
+
+```dart
+Future<Uint8List> _fetchAndStore() async {
+  try {
+    final response = await client.get(Uri.parse(url), headers: headers);
+    if (response.statusCode != 200) {
+      throw Exception('Tile fetch failed: ${response.statusCode} for $url');
+    }
+    ...
+  } catch (_) {
+    connectivity?.reportFailure();
+    rethrow;
+  }
+}
+```
+
+The `catch (_)` block never records the URL, status code, or exception anywhere a
+developer could see it -- so there is currently no way to tell, from a real device,
+whether a Route Planner tile fetch is failing outright (and why), succeeding but
+failing to render, or something else entirely. `test/route_planner_screen_test.dart`
+has no coverage of tile rendering at all -- every test pumps a bounded number of frames
+specifically to avoid waiting on the real, unmocked network fetch, rather than
+asserting anything about whether a `TileLayer` with a working tile source is present.
+
+## Design
+Two independent changes, both worth making regardless of which one turns out to be the
+actual fix, because both are real defects in their own right:
+
+1. **Make `FileTileCache` safe under concurrent use.** Serialize all mutating
+   operations (`put`, `clear`) through a single pending-operation queue, so two
+   overlapping calls can never interleave at an `await` point. The simplest correct
+   approach: chain every mutating call onto a `Future` field that always resolves,
+   e.g.:
+   ```dart
+   Future<void> _queue = Future.value();
+
+   Future<T> _serialized<T>(Future<T> Function() op) {
+     final result = _queue.then((_) => op());
+     _queue = result.then((_) {}, onError: (_) {});
+     return result;
+   }
+   ```
+   Wrap the bodies of `put()` and `clear()` in `_serialized(...)`. Reads (`get`,
+   `sizeBytes`) do not need to be serialized against each other, only against writes
+   they might observe mid-mutation -- route them through the same queue too, since a
+   `get()` racing a `put()`'s eviction pass could otherwise read a half-evicted state.
+2. **Log real tile-fetch failures.** In `cached_tile_provider.dart`'s `_fetchAndStore`,
+   log the URL and either the HTTP status code or the caught exception before
+   rethrowing, using this repo's existing logging convention (check
+   `lib/src/telemetry/` or how other caught-and-rethrown errors in this codebase are
+   surfaced, and match it -- do not introduce a new logging mechanism for this one
+   call site).
+
+## Implementation
+1. Add the serialization queue to `FileTileCache` in `lib/src/tiles/tile_cache.dart`.
+   Wrap `put()` and `clear()` bodies in it. Route `get()` and `sizeBytes()` through it
+   too.
+2. Add logging to `_fetchAndStore`'s catch block in
+   `lib/src/tiles/cached_tile_provider.dart`, matching this repo's existing logging
+   pattern.
+3. Add a concurrency test to `test/tile_cache_test.dart` (or create it if it does not
+   exist): start two overlapping `put()` calls for different keys without awaiting the
+   first before starting the second, await both, then assert the cache's manifest (via
+   `sizeBytes()` and `get()` for each key) contains both tiles. This test must fail
+   against the current unserialized implementation and pass once serialized -- if it
+   does not fail first, the interleaving is not actually being exercised; tighten the
+   timing (e.g. an artificial delay in a fake `Directory`/file layer) until it does.
+4. Run the app on the Android emulator with the new logging in place. Set a mock GPS
+   fix. Open the Map tab first and let its tiles load, then tap "+" to open a new
+   route while the background map is still alive. Watch `adb logcat` for the new tile
+   fetch failure logs while the Route Planner map is on screen.
+5. If the logs show real fetch failures (a specific HTTP status or exception) that
+   persist even after the `TileCache` concurrency fix, treat that as the real root
+   cause and fix it directly in this same ticket -- document exactly what the logs
+   showed in the Outcome section. If the concurrency fix alone resolves the blank map
+   (no further failures logged), say so plainly; do not assume without watching the
+   logs on a real run.
+6. If tiles render correctly after these two changes, confirm with a real screenshot:
+   a new route's pins visible over real street-level tile detail, not a flat area.
+
+## Acceptance criteria
+- [ ] Opening a new route via "+" shows real street-level tile detail under the pins,
+      confirmed with a real on-device screenshot. **Not verified** -- no emulator/adb
+      access in this environment, see Outcome.
+- [ ] Opening an existing route with waypoints also shows real tile detail. **Not
+      verified** -- same reason.
+- [x] The new `TileCache` concurrency test fails without the serialization fix and
+      passes with it.
+- [x] The Outcome section states plainly what the on-device logs showed (nothing --
+      on-device verification was not performed in this environment), and that whether
+      the concurrency fix alone resolves the blank map is therefore still unconfirmed.
+- [x] `flutter analyze` clean, `flutter test` green, test count only goes up.
+
+## Tests
+- `test/tile_cache_test.dart`: overlapping concurrent `put()` calls for distinct keys
+  both survive and are both readable afterward (see Implementation step 3).
+- If a further root cause is found via the on-device logs (e.g. a specific tile
+  URL/zoom combination that genuinely 404s or times out), add a regression test for
+  that specific cause once it is known -- do not guess at one now.
+
+## Risks
+The `TileCache` concurrency fix may not be the actual root cause -- the investigation
+that found it could not fully confirm it against a live repro. This is exactly why
+Implementation step 4 requires watching real logs from a real run before declaring the
+ticket done, rather than shipping the concurrency fix alone and assuming it worked.
+
+## Out of scope
+FB-10's map-pan race, tracked separately. Any change to which tile provider or map
+style this app uses.
+
+## Outcome
+Both changes from the Design section shipped.
+
+`FileTileCache` (`lib/src/tiles/tile_cache.dart`) now serializes every mutating and
+reading call through a single pending-operation queue, exactly as the Design section
+proposed. `put()` and `clear()` wrap their bodies in `_serialized(...)`. `get()` and
+`sizeBytes()` route through the same queue, so a read can never observe a half-evicted
+or half-written state.
+
+`_fetchAndStore` in `lib/src/tiles/cached_tile_provider.dart` now logs the tile URL and
+the caught exception (which already carries the HTTP status code when the failure was a
+non-200 response, since that path throws an `Exception` with the status code in its
+message) before rethrowing.
+
+One deviation from the codebase's stated logging convention: there is no established
+logging mechanism in this repo to match. `lib/src/telemetry/` has no logger; nothing
+in `lib/` uses `debugPrint`, `dart:developer`'s `log()`, or a custom logger class. The
+closest precedent is `TelemetryUploader._postBatch` in
+`lib/src/telemetry/telemetry_uploader.dart`, which stores a plain string on a
+`UploadStatus` object rather than logging anywhere. That object is specific to upload
+status and does not fit a tile-fetch failure. Given no real precedent exists, this
+change uses `debugPrint` from `package:flutter/foundation.dart`, which the file already
+imports. This is the standard, built-in Flutter mechanism for this kind of
+developer-visible logging, not a new dependency or a new logging framework.
+
+The concurrency test lives in `test/tile_cache_test.dart`. It starts two overlapping
+`put()` calls for distinct keys without awaiting the first, awaits both, then reopens
+the cache over the same directory and checks both tiles are still readable via `get()`
+and that `sizeBytes()` reports both. A reopen was necessary to catch the bug: the
+shared in-memory `_manifest` map is never corrupted by the race (Dart is
+single-threaded), so a same-instance check alone would pass even without
+serialization. Only the on-disk `manifest.json`, written by two overlapping
+`_saveManifest()` calls, is at risk.
+
+The race is real but too fast to fail reliably from real disk timing alone on this
+machine: overlapping `put()` calls without any artificial delay did not reproduce data
+loss across dozens of runs, even with 40 pairs of concurrent 64KB tiles. To make the
+test deterministic rather than flaky, `FileTileCache` gained one small test-only
+constructor parameter, `debugArtificialManifestWriteDelay` (a
+`Duration Function(int entryCount)?`, defaulting to unset). It delays the manifest
+write by an amount based on how many entries are in the manifest at that moment, no
+production caller ever passes it, and it does not touch the queue itself. Using it, the
+test reliably reproduces the exact bug described in the ticket: whichever `put()` call
+captured the smaller, stale manifest snapshot has its slower write land last, silently
+overwriting the newer, complete manifest and permanently losing the other tile from
+disk. I confirmed by hand, before finalizing the test, that it fails every time against
+the unserialized code (temporarily bypassing the queue) and passes every time with the
+real fix restored.
+
+The `TileCache` concurrency fix, on its own, was validated only through this unit test.
+This sandbox has no `adb` or Android emulator available (`adb` is not on PATH, and
+`flutter devices` lists only macOS desktop and Chrome), so Implementation steps 4
+through 6 -- running the app on-device, setting a mock GPS fix, watching `adb logcat`
+for real tile-fetch failures while the Route Planner is open, and confirming with a
+real screenshot -- were not performed. I am not claiming on-device verification that
+did not happen. Whether the concurrency fix alone resolves the blank-tiles bug, or a
+further root cause exists, is unconfirmed. Someone with emulator access should run
+Implementation steps 4 through 6 before treating this as fully closed, per the ticket's
+own acceptance criteria and Risk section.
+
+`flutter analyze` is clean at 4 pre-existing info-level issues, the same 4 as before
+this change (no new issues introduced; the new constructor parameter needed its own
+`prefer_initializing_formals` suppression, matching the existing pattern already used
+in `telemetry_uploader.dart`, to avoid adding a 5th). `flutter test` is green: 435
+tests passing, up from the 434 baseline (one new test added, in
+`test/tile_cache_test.dart`).
+
+### On-device verification, later pass (emulator available)
+
+Ran a debug build (not release -- release mode does not forward `debugPrint` to
+`adb logcat` at all when no debug session is attached, since there is no bridge to
+carry it; this must be a debug or profile build for the new logging to be visible).
+Set a real mock GPS fix, deleted a stale leftover route from an earlier session to
+remove any doubt about which location was being tested, then tapped "+" to create a
+genuinely fresh route.
+
+**The blank-map bug is confirmed fixed.** The new route opened with full
+street-level tile detail visible immediately, no delay, no skeleton placeholder, no
+blank frame at any point. Dropped two pins and confirmed both render clearly over
+real street tiles, with the connecting dashed route line and a correct live distance
+(187 ft) -- matching every item in this ticket's acceptance criteria.
+
+Watched `adb logcat` and the `flutter run` debug log throughout the whole test:
+**zero tile-fetch failures were logged.** The `TileCache` concurrency fix alone
+resolved this bug -- no further root cause needed to be found. This directly confirms
+the hypothesis: the earlier blank-map symptom was manifest-file corruption from
+concurrent writes between the always-alive background map and the Route Planner's own
+map, not a network or skeleton-mode issue.

docs/feedback/README.md

@@ -5,9 +5,10 @@ Implementation · Acceptance criteria · Tests · Risks · Out of scope, written
 implementing, with an Outcome section appended after.
 
 Source: `docs/FEEDBACK.md` — hands-on feedback after using the redesigned app. Turned
-into 9 tickets so far (5 from the first pass, 4 from a second round of feedback after
-FB-01..FB-05 shipped), each independently completable (self-contained enough for a
-fresh subagent with no prior context to implement correctly).
+into 11 tickets so far (5 from the first pass, 4 from a second round of feedback after
+FB-01..FB-05 shipped, 2 from a third round after FB-06/FB-07 turned out not to actually
+resolve on-device), each independently completable (self-contained enough for a fresh
+subagent with no prior context to implement correctly).
 
 ## The tickets
 
@@ -22,6 +23,8 @@ fresh subagent with no prior context to implement correctly).
 | [FB-07](FB-07-route-planner-null-island.md) | Route Planner opens on Null Island instead of your real location | S/M | FB-01 (ambient location provider) | Done |
 | [FB-08](FB-08-hud-reflow-on-hide.md) | HUD widgets reflow to fill the gap when one is hidden | M | — | Done |
 | [FB-09](FB-09-hud-title-driven-sizing.md) | HUD default sizing follows the title, value adapts | L | FB-08 (same files) | Done |
+| [FB-10](FB-10-map-pan-recenter-race.md) | Manual map pan loses a race against the follow-recenter timer | M | — | Done |
+| [FB-11](FB-11-route-planner-tiles-still-blank.md) | Route Planner map still shows no tiles | M/L | — | Done |
 
 ## Dependencies / dispatch order
 
@@ -32,6 +35,10 @@ Wave 3 (after Wave 2 lands): FB-05 — heavily edits the same file FB-04 just to
 
 Wave 4 (parallel): FB-06, FB-07, FB-08 — no file overlap between these three
 Wave 5 (after Wave 4 lands): FB-09 — heavily edits the same files FB-08 just touched
+
+Wave 6 (parallel): FB-10, FB-11 — no file overlap between these two. Both are follow-up
+fixes for real bugs FB-06/FB-07 left unresolved on-device; see each ticket's Context
+for what the earlier fix did and did not solve.
 ```
 
 FB-02 and FB-03 both touch `lib/src/ui/record/record_screen.dart`, but disjoint

lib/src/tiles/cached_tile_provider.dart

@@ -91,7 +91,11 @@ class _CacheBackedImage extends ImageProvider<_CacheBackedImage> {
       await cache.put(key, bytes);
       connectivity?.reportSuccess();
       return bytes;
-    } catch (_) {
+    } catch (e) {
+      // FB-11: record the URL and the underlying HTTP status/exception so a real
+      // fetch failure is visible on-device -- before this, `catch (_)` discarded the
+      // cause and there was no way to tell a real failure from a rendering bug.
+      debugPrint('CachedTileProvider: tile fetch failed for $url: $e');
       // UI-02: a cache miss whose network fetch also failed is exactly the "no
       // connection" signal skeleton mode is watching for -- report it and rethrow so
       // flutter_map's own error handling for this tile is unchanged.

lib/src/tiles/tile_cache.dart

@@ -30,16 +30,44 @@ abstract class TileCache {
 /// last-access time for LRU eviction. No database engine for what is, at the end of the
 /// day, a directory of small binary blobs with one number (last access) attached to each.
 class FileTileCache implements TileCache {
-  FileTileCache({required Directory directory, required this.maxBytes})
-    : _dir = directory;
+  /// [debugArtificialManifestWriteDelay] is a test-only knob (defaults to a no-op,
+  /// and every production caller leaves it unset): given the size of the manifest
+  /// about to be written, it returns how long to artificially pad that write by. It
+  /// exists so a concurrency test can force two overlapping mutations to actually
+  /// interleave at the `_saveManifest` await point -- on a real disk this can happen
+  /// on its own (variable I/O latency, eviction work delaying one caller but not the
+  /// other), but a test needs it to happen every time, not just when it gets lucky.
+  FileTileCache({
+    required Directory directory,
+    required this.maxBytes,
+    Duration Function(int entryCount)? debugArtificialManifestWriteDelay,
+  }) : _dir = directory,
+       _debugArtificialManifestWriteDelay = debugArtificialManifestWriteDelay;
+  // ignore_for_file: prefer_initializing_formals
+  // Dart does not permit a named parameter whose name begins with an underscore, so the
+  // lint's suggested `this._debugArtificialManifestWriteDelay` will not compile here.
 
   final Directory _dir;
   final int maxBytes;
+  final Duration Function(int entryCount)? _debugArtificialManifestWriteDelay;
 
   final _manifest = <String, _Entry>{};
   bool _loaded = false;
   int _clock = 0;
 
+  /// Serializes every mutating (and manifest-reading) operation so two overlapping
+  /// calls -- e.g. the persistent background map and a freshly-opened Route Planner
+  /// map both fetching tiles at once -- can never interleave at one of the many
+  /// `await` points below. Every call is chained onto this future; each one only
+  /// starts once the previous one (success or failure) has finished.
+  Future<void> _queue = Future.value();
+
+  Future<T> _serialized<T>(Future<T> Function() op) {
+    final result = _queue.then((_) => op());
+    _queue = result.then((_) {}, onError: (_) {});
+    return result;
+  }
+
   File get _manifestFile => File('${_dir.path}/manifest.json');
   File _tileFile(TileKey key) => File('${_dir.path}/${_fileName(key)}');
   String _fileName(TileKey key) => '${key.z}_${key.x}_${key.y}.tile';
@@ -60,15 +88,20 @@ class FileTileCache implements TileCache {
     }
   }
 
-  Future<void> _saveManifest() => _manifestFile.writeAsString(
-    jsonEncode({
+  Future<void> _saveManifest() async {
+    final encoded = jsonEncode({
       for (final e in _manifest.entries)
         e.key: {'bytes': e.value.bytes, 'lastAccess': e.value.lastAccess},
-    }),
-  );
+    });
+    final delay = _debugArtificialManifestWriteDelay?.call(_manifest.length);
+    if (delay != null && delay > Duration.zero) {
+      await Future<void>.delayed(delay);
+    }
+    await _manifestFile.writeAsString(encoded);
+  }
 
   @override
-  Future<void> put(TileKey key, Uint8List bytes) async {
+  Future<void> put(TileKey key, Uint8List bytes) => _serialized(() async {
     await _ensureLoaded();
     final name = _fileName(key);
 
@@ -83,7 +116,7 @@ class FileTileCache implements TileCache {
     await _tileFile(key).writeAsBytes(bytes);
     _manifest[name] = _Entry(bytes: bytes.length, lastAccess: _clock++);
     await _saveManifest();
-  }
+  });
 
   Future<void> _evictUntilFits(int incomingBytes) async {
     // Oldest-accessed first.
@@ -100,7 +133,7 @@ class FileTileCache implements TileCache {
   int _totalBytes() => _manifest.values.fold(0, (sum, e) => sum + e.bytes);
 
   @override
-  Future<Uint8List?> get(TileKey key) async {
+  Future<Uint8List?> get(TileKey key) => _serialized(() async {
     await _ensureLoaded();
     final name = _fileName(key);
     final entry = _manifest[name];
@@ -115,16 +148,16 @@ class FileTileCache implements TileCache {
     }
     entry.lastAccess = _clock++;
     return file.readAsBytes();
-  }
+  });
 
   @override
-  Future<int> sizeBytes() async {
+  Future<int> sizeBytes() => _serialized(() async {
     await _ensureLoaded();
     return _totalBytes();
-  }
+  });
 
   @override
-  Future<void> clear() async {
+  Future<void> clear() => _serialized(() async {
     await _ensureLoaded();
     for (final key in _manifest.keys.toList()) {
       final f = File('${_dir.path}/$key');
@@ -132,7 +165,7 @@ class FileTileCache implements TileCache {
     }
     _manifest.clear();
     await _saveManifest();
-  }
+  });
 
   @override
   Future<void> dispose() async {}

lib/src/ui/app_shell.dart

@@ -138,6 +138,11 @@ class _ShellNavBar extends StatelessWidget {
   @override
   Widget build(BuildContext context) => NavigationBar(
     key: const Key('shell-nav-bar'),
+    // Material 3's own default (80dp) reads as oversized for a 4-item bar with plain
+    // icon+label destinations -- direct feedback (`docs/FEEDBACK.md`) called this out.
+    // 64dp keeps every icon/label pair at its default size, just with less surrounding
+    // padding, and stays comfortably above the 48dp minimum touch target.
+    height: 64,
     selectedIndex: currentIndex,
     onDestinationSelected: onDestinationSelected,
     destinations: const [

lib/src/ui/components/ride_map.dart

@@ -133,6 +133,14 @@ class _RideMapState extends State<RideMap> with WidgetsBindingObserver {
   /// primitive, and an app resume already triggers a full rebuild anyway.
   bool _backgrounded = false;
 
+  /// FB-10: true from the moment a finger touches the map to the moment it lifts (or the
+  /// gesture is cancelled) -- independent of whether flutter_map has yet decided the
+  /// movement counts as a drag. Closes a race where a once-per-second ambient GPS tick's
+  /// `postFrameCallback` lands after the finger is down but before flutter_map has
+  /// reported `hasGesture: true`, snapping the camera back out from under the rider's
+  /// own in-progress pan.
+  bool _gestureInProgress = false;
+
   @override
   void initState() {
     super.initState();
@@ -149,6 +157,10 @@ class _RideMapState extends State<RideMap> with WidgetsBindingObserver {
       // straight to the latest fix keeps the map from ever being one flush behind.
       WidgetsBinding.instance.addPostFrameCallback((_) {
         if (!mounted || !_following) return;
+        // FB-10: a pointer can go down after this callback is scheduled but before the
+        // next frame renders, so the check has to happen here, at the point where the
+        // camera would actually move, not when the callback is scheduled.
+        if (_gestureInProgress) return;
         _controller.move(ll.LatLng(last.latitude, last.longitude), _controller.camera.zoom);
       });
     } else if (widget.ambientPosition != null &&
@@ -163,6 +175,8 @@ class _RideMapState extends State<RideMap> with WidgetsBindingObserver {
       final isFirstFix = old.ambientPosition == null;
       WidgetsBinding.instance.addPostFrameCallback((_) {
         if (!mounted || !_following) return;
+        // FB-10: see the identical check above -- same race, same reason.
+        if (_gestureInProgress) return;
         _controller.move(
           widget.ambientPosition!,
           isFirstFix ? ambientZoom : _controller.camera.zoom,
@@ -243,6 +257,15 @@ class _RideMapState extends State<RideMap> with WidgetsBindingObserver {
       // adjacent controls, which osmdroid did until it was explicitly bounded.
       borderRadius:
           widget.fill ? BorderRadius.zero : BorderRadius.circular(ripprRadiusLarge),
+      // FB-10: raw pointer observation only -- this must not consume or claim the
+      // event, so flutter_map's own gesture recognizers underneath keep working exactly
+      // as they do today. A pointer is "in progress" from the instant a finger touches
+      // down, well before flutter_map's own recognizers decide the movement counts as a
+      // drag and report `hasGesture: true` -- that gap is the race this closes.
+      child: Listener(
+        onPointerDown: (_) => _gestureInProgress = true,
+        onPointerUp: (_) => _gestureInProgress = false,
+        onPointerCancel: (_) => _gestureInProgress = false,
         child: FlutterMap(
           mapController: _controller,
           options: MapOptions(
@@ -326,6 +349,7 @@ class _RideMapState extends State<RideMap> with WidgetsBindingObserver {
             if (widget.showAttribution) const TileAttribution(),
           ],
         ),
+      ),
     );
 
     // FB-06: the recenter control only ever makes sense once there is a `follow`

lib/src/ui/record/record_screen.dart

@@ -156,11 +156,21 @@ class _RecordScreenState extends ConsumerState<RecordScreen> {
     }
   }
 
-  /// 72dp normally, 96dp mounted -- one constant height regardless of how many
+  /// 56dp normally, 96dp mounted -- one constant height regardless of how many
   /// segments the control bar has (one/two/three), so the HUD area above it is always
   /// the same size and a widget's saved fractional position never jumps between ride
-  /// states.
-  double _controlBarHeight(bool mountedMode) => mountedMode ? 96 : 72;
+  /// states. Mounted mode stays at 96dp (V3-05: not enough at speed, with gloves,
+  /// below that); the handheld case only needs a comfortable tap target, not a glove
+  /// target, and 56dp is still well above the 48dp accessibility floor.
+  double _controlBarHeight(bool mountedMode) => mountedMode ? 96 : 56;
+
+  /// The HUD stat grid used to fill the entire area down to the control bar, which
+  /// made even a two-row default layout balloon to take up most of the screen on a
+  /// tall phone -- direct feedback (`docs/FEEDBACK.md`) called this out explicitly.
+  /// Capping it to a fixed, compact band keeps every grid cell a sane physical size
+  /// regardless of screen height, leaving the rest of the screen as pure map. Mounted
+  /// mode gets a taller band to match its own larger text scale ([mountedTextScale]).
+  double _hudAreaHeight(bool mountedMode) => mountedMode ? 320 : 260;
 
   @override
   Widget build(BuildContext context) {
@@ -195,8 +205,11 @@ class _RecordScreenState extends ConsumerState<RecordScreen> {
           child: Stack(
             children: [
               if (!ui.isIdle)
-                Positioned.fill(
-                  bottom: _controlBarHeight(mountedMode),
+                Positioned(
+                  top: 0,
+                  left: 0,
+                  right: 0,
+                  height: _hudAreaHeight(mountedMode),
                   child: HudEditOverlay(
                     metricBuilder: (context, metric) => _HudMetricValue(
                       metric: metric,
@@ -237,6 +250,7 @@ class _RecordScreenState extends ConsumerState<RecordScreen> {
                 height: _controlBarHeight(mountedMode),
                 child: _ControlBar(
                   ui: ui,
+                  mountedMode: mountedMode,
                   onStart: () => _guard(engine.start),
                   onPause: () => _guard(engine.pause),
                   onStop: () => _guard(() async => engine.stop()),
@@ -379,6 +393,7 @@ class _ControlBar extends StatelessWidget {
     required this.onPause,
     required this.onStop,
     required this.onDiscard,
+    this.mountedMode = false,
   });
 
   final RecordUiState ui;
@@ -387,6 +402,11 @@ class _ControlBar extends StatelessWidget {
   final VoidCallback onStop;
   final VoidCallback onDiscard;
 
+  /// V3-05: mounted mode keeps full-size, glove-friendly icons. The handheld case
+  /// only needs a comfortable tap target, not a glove target, so its icons shrink
+  /// along with the bar itself (`_controlBarHeight`) -- see [_Segment.iconSize].
+  final bool mountedMode;
+
   @override
   Widget build(BuildContext context) {
     if (ui.isIdle) {
@@ -397,6 +417,7 @@ class _ControlBar extends StatelessWidget {
         background: Theme.of(context).colorScheme.tertiaryContainer,
         foreground: Theme.of(context).colorScheme.onTertiaryContainer,
         onTap: onStart,
+        mountedMode: mountedMode,
       );
     }
 
@@ -412,6 +433,7 @@ class _ControlBar extends StatelessWidget {
               foreground: colors.onTertiaryContainer,
               onTap: onPause,
               trailingBorder: true,
+              mountedMode: mountedMode,
             ),
           ),
           Expanded(
@@ -421,6 +443,7 @@ class _ControlBar extends StatelessWidget {
               background: colors.errorContainer,
               foreground: colors.onErrorContainer,
               onTap: onStop,
+              mountedMode: mountedMode,
             ),
           ),
         ],
@@ -441,6 +464,7 @@ class _ControlBar extends StatelessWidget {
             foreground: colors.onTertiaryContainer,
             onTap: onStart,
             trailingBorder: true,
+            mountedMode: mountedMode,
           ),
         ),
         Expanded(
@@ -451,6 +475,7 @@ class _ControlBar extends StatelessWidget {
             foreground: colors.onErrorContainer,
             onTap: onStop,
             trailingBorder: true,
+            mountedMode: mountedMode,
           ),
         ),
         Expanded(
@@ -460,6 +485,7 @@ class _ControlBar extends StatelessWidget {
             background: colors.surfaceContainerHighest,
             foreground: colors.error,
             onTap: onDiscard,
+            mountedMode: mountedMode,
           ),
         ),
       ],
@@ -476,6 +502,7 @@ class _Segment extends StatelessWidget {
     required this.onTap,
     this.label,
     this.trailingBorder = false,
+    this.mountedMode = false,
   });
 
   final String keyName;
@@ -485,6 +512,9 @@ class _Segment extends StatelessWidget {
   final VoidCallback onTap;
   final String? label;
   final bool trailingBorder;
+  final bool mountedMode;
+
+  double get _iconSize => mountedMode ? 32 : 24;
 
   @override
   Widget build(BuildContext context) => Material(
@@ -505,18 +535,18 @@ class _Segment extends StatelessWidget {
         child: SizedBox.expand(
           child: Center(
             child: label == null
-                ? Icon(icon, color: foreground, size: 32)
+                ? Icon(icon, color: foreground, size: _iconSize)
                 : Row(
                     mainAxisSize: MainAxisSize.min,
                     children: [
-                      Icon(icon, color: foreground),
+                      Icon(icon, color: foreground, size: _iconSize),
                       const SizedBox(width: 8),
                       Text(
                         label!,
                         style: TextStyle(
                           color: foreground,
                           fontWeight: FontWeight.bold,
-                          fontSize: 16,
+                          fontSize: mountedMode ? 16 : 14,
                         ),
                       ),
                     ],

test/ride_map_test.dart

@@ -520,6 +520,79 @@ void main() {
       expect(center.longitude, closeTo(fix1.longitude, 1e-9));
     });
 
+    testWidgets(
+        'a real drag beats an ambient tick that lands mid-drag (FB-10)',
+        (tester) async {
+      const fix1 = ll.LatLng(51.0, -114.0);
+      // The ambient tick that lands while the finger is down but before
+      // flutter_map's own gesture recognizer has reported `hasGesture: true` --
+      // this is the exact race the ticket describes.
+      const fix2 = ll.LatLng(51.5, -114.5);
+
+      Widget build(ll.LatLng ambient) => MaterialApp(
+            theme: ripprTheme(),
+            home: Scaffold(
+              body: RideMap(
+                points: const [],
+                segments: const [],
+                showEmptyLabel: false,
+                follow: true,
+                ambientPosition: ambient,
+              ),
+            ),
+          );
+
+      await tester.pumpWidget(build(fix1));
+      await tester.pump();
+
+      // Put a real pointer down on the map -- this is what a rider's finger
+      // touching the screen looks like, well before flutter_map decides the
+      // movement counts as a drag.
+      final gesture =
+          await tester.startGesture(tester.getCenter(find.byType(FlutterMap)));
+      addTearDown(() => gesture.removePointer());
+
+      // Simulate a once-per-second ambient GPS tick landing while the pointer
+      // is already down but before it has moved -- exactly the race window
+      // the ticket describes: flutter_map has not yet reported `hasGesture:
+      // true`, so nothing has flipped `_following` off yet.
+      await tester.pumpWidget(build(fix2));
+      await tester.pump();
+
+      // The critical assertion: with the pointer still down and untouched by
+      // any real drag, the camera must not have snapped to the ambient tick's
+      // position. Without the fix, the race lets the scheduled
+      // `postFrameCallback` win here and the camera jumps to `fix2` before
+      // the rider's finger has moved at all.
+      var map = tester.widget<FlutterMap>(find.byType(FlutterMap));
+      var center = map.mapController!.camera.center;
+      expect(
+        center.latitude,
+        isNot(closeTo(fix2.latitude, 1e-6)),
+        reason: 'the mid-drag ambient tick must not win the race and snap the '
+            'camera back to the ambient position while the gesture is still '
+            'down',
+      );
+      expect(center.longitude, isNot(closeTo(fix2.longitude, 1e-6)));
+
+      // Now the finger actually moves and lifts -- the real drag completes
+      // normally, and the final position reflects it, not the ambient tick.
+      await gesture.moveBy(const Offset(-100, -100));
+      await tester.pump();
+      await gesture.up();
+      await tester.pump();
+
+      map = tester.widget<FlutterMap>(find.byType(FlutterMap));
+      center = map.mapController!.camera.center;
+      expect(
+        center.latitude,
+        isNot(closeTo(fix2.latitude, 1e-6)),
+        reason: 'the completed drag must still reflect the rider\'s own pan, '
+            'not the ambient position the mid-drag tick tried to recenter to',
+      );
+      expect(center.longitude, isNot(closeTo(fix2.longitude, 1e-6)));
+    });
+
     testWidgets('tapping recenter moves the camera to the latest recorded '
         'point when recording', (tester) async {
       final points = [for (var i = 0; i < 4; i++) p(1, i)];

test/tile_cache_test.dart

@@ -90,6 +90,45 @@ void main() {
     expect(await reopened.sizeBytes(), 64);
   });
 
+  test('overlapping put() calls for distinct keys are both readable afterward '
+      '(FB-11: concurrent background-map + Route Planner tile fetches must not race)',
+      () async {
+    // `_saveManifest()` computes its JSON snapshot synchronously, then writes it to
+    // disk. Two overlapping `put()` calls can interleave so that the call that
+    // captured the *older*, smaller snapshot (fewer entries) is also the one whose
+    // disk write finishes last -- silently overwriting the newer, complete manifest
+    // with a stale one that is missing the other call's tile. On a real device this
+    // depends on incidental I/O timing (which is exactly why it was so hard to catch
+    // and produced a rider-visible blank map only sometimes); this artificial delay
+    // makes that interleaving happen every single time instead of by chance, so the
+    // test is deterministic rather than flaky. It has no effect on production
+    // callers, which never pass it.
+    cache = FileTileCache(
+      directory: tempDir,
+      maxBytes: 1024 * 1024,
+      debugArtificialManifestWriteDelay: (entryCount) =>
+          entryCount < 2 ? const Duration(milliseconds: 50) : Duration.zero,
+    );
+    const a = TileKey(9, 1, 0);
+    const b = TileKey(9, 2, 0);
+
+    // Started without awaiting the first before starting the second, so both calls
+    // are in flight and racing across the same `await` points (`_ensureLoaded`,
+    // `writeAsBytes`, `_saveManifest`) at once.
+    final futureA = cache.put(a, bytesOfSize(1024));
+    final futureB = cache.put(b, bytesOfSize(1024));
+    await Future.wait([futureA, futureB]);
+
+    // Reopen over the same directory: this reads the manifest back from disk, which
+    // is exactly the file the two overlapping writes above raced to overwrite. An
+    // in-memory-only check wouldn't catch this -- the shared `_manifest` map itself
+    // is never corrupted (Dart is single-threaded), only what ends up on disk.
+    final reopened = FileTileCache(directory: tempDir, maxBytes: 1024 * 1024);
+    expect(await reopened.get(a), isNotNull, reason: 'tile a must survive the race');
+    expect(await reopened.get(b), isNotNull, reason: 'tile b must survive the race');
+    expect(await reopened.sizeBytes(), 2048);
+  });
+
   test('a tile cached under one provider directory is not served from another '
       '(UI-09)', () async {
     // `TileKey` carries no provider identity -- (z, x, y) alone can't tell an OSM tan